# std::expected<T,E>::emplace

From cppreference.com
< cpp‎ | utility‎ | expected

Primary template |  |
template< class... Args > constexpr T& emplace( Args&&... args ) noexcept; | (1) | (since C++23)
template< class U, class... Args > constexpr T& emplace( std::initializer_list<U> il, Args&&... args ) noexcept; | (2) | (since C++23)
void partial specialization |  |
constexpr void emplace() noexcept; | (3) | (since C++23)

Constructs an expected value in-place. After the call, `has_value()` returns true.

1) Destroys the contained value, then direct-initializes the expected value contained in *this with std::forward<Args>(args)....
This overload participates in overload resolution only if std::is_nothrow_constructible_v<T, Args...> is true.
2) Destroys the contained value, then direct-initializes the expected value contained in *this with il and std::forward<Args>(args)....
This overload participates in overload resolution only if std::is_nothrow_constructible_v<T, std::initializer_list<U>&, Args...> is true.
3) If *this contains an unexpected value, destroys that value.

### Parameters

args | - | the arguments to pass to the constructor
il | - | the initializer list to pass to the constructor

### Return value

1) *std::construct_at(std::addressof(`val`), std::forward<Args>(args)...)
2) *std::construct_at(std::addressof(`val`), il, std::forward<Args>(args)...)

### Notes

If the construction of `T` is potentially-throwing, `operator=` can be used instead.

### Example

| This section is incomplete Reason: no example

### See also

operator= | assigns contents (public member function)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/utility/expected/emplace&oldid=173295"